1. Field of the Invention
The present invention relates to an apparatus and method for supporting and transporting steel during processing. More particularly, the present invention relates to an apparatus and method for protecting steel slabs during transport through a slab heating furnace.
2 . Description of the Invention Background
During processing, steel slabs often must be brought to elevated temperatures so that the steel may be hot worked. For example, slabs of certain types of stainless steel are heated to temperatures in the range of 1950.degree. F. to 2350.degree. F. for hot rolling into coils. The steel slabs may be brought to the required elevated temperature by passing the slabs through a reheat furnace. The slabs may be in the as-cast or the ground surface condition.
To facilitate movement of the heavy slabs into and out of the reheat furnace and minimize the contact with the slab surface, pathways of parallel, raised support members, referred to as "skid bars", may be used In a representative skid bar system, illustrated in FIG. 1, the steel slabs 5 are pushed into the reheat furnace 10 along four raised, parallel skid bar rails 15. While in the furnace, the steel slabs 5 ride on skid bars made of metal. Near the furnace exit, the slabs sit on a solid refractory base to permit the slab temperature to equalize. On exiting the furnace, the slab 5 is pushed back on to the four rails and is dropped out onto table rolls to carry the slab to the hot strip mill. Normally, the skid bars are water-cooled to protect the skid bars, but which also tends to remove heat from the areas of the slab which contact the skid bars.
Although the skid bar system aids in transporting the steel slabs and reduces contact with the slab surface, the skid bars themselves may damage the surface of the slabs. Slabs of certain types of steel, such as ferritic stainless steel, are relatively more susceptible to physical marking on the slab's bottom surface when the slab slides over the skid bars. The marks may be carried onto the surface of the coil when the slab is subsequently hot rolled. The marked coil surface must then be conditioned to remove the marks. Conditioning is an additional, costly processing step which decreases yield and increases the cost of the finished product.
To prevent slab marking, it is known in the stainless steel industry to use sacrificial sheet metal riders between the skid bars and the slab surfaces. However, because of the materials used therein and the particular construction thereof, some skid bar systems do not allow for use of such sheet metal riders.
From the foregoing, it is apparent that there is a need for a device which will protect steel slabs from skid bar marking during the slab's movement through a slab heating furnace. Accordingly, it is an object of the invention to provide an apparatus which will support a steel slab and protect the surface of the steel slab while it advances over skid bars.